As taught in U.S. Pat. No. 6,001,069, catheters can be used to treat human blood vessels that have become partially or completely occluded by plaque, thrombi, emboli or other substances that reduce the blood carrying capacity of the vessel. To remove or reduce the occlusion, the catheter is used to deliver solutions containing therapeutic compounds directly to the occlusion site. In these particular applications, ultrasonic energy generated by the ultrasound assembly is used to enhance the effect of the therapeutic compounds. Such a device can be used in the treatment of diseases such as peripheral arterial occlusion or deep vein thrombosis. In such applications, the ultrasonic energy enhances treatment of the occlusion with therapeutic compounds such as urokinase, tissue plasminogen activator (“tPA”), recombinant tissue plasminogen activator (“rtPA”) and the like. Further information on enhancing the effect of a therapeutic compound using ultrasonic energy is provided in U.S. Pat. Nos. 5,318,014, 5,362,309, 5,474,531, 5,628,728, 6,001,069 and 6,210,356.
The efficacy of therapeutic compounds in reducing or removing a vascular occlusion can also be enhanced by increasing the temperature of the therapeutic compound that is provided at the treatment site. For example, it has been determined that treatment of lower limb ischemia progresses more rapidly when heated rtPA is used, than when room temperature rtPA is used. See Dimitrios K. Tsetis et al., “Potential Benefits From Heating the High-Dose rtPA Boluses Used in Catheter-Directed Thrombolysis for Acute/Subacute Lower Limb Ischemia”, J Endovasc Ther 10:739–744 (2003), the entire disclosure of which is hereby incorporated herein by reference.